A semiconductor manufacturing process includes a step of conveying a plurality of semiconductor wafers at once from a foup that houses the plurality of semiconductor wafers lined up in an upper-lower direction to a processing shelf in which the semiconductor wafers are subjected to predetermined processing. While the semiconductor wafers are being conveyed, the upper-lower interval (hereinafter referred to as a “pitch”) between the adjacent semiconductor wafers may be changed. A pitch changing mechanism is used to change this pitch.
A conventional pitch changing mechanism includes: a plurality of wafer holding trays each configured to receive the entire lower surface of the semiconductor wafer; and vertical shafts respectively provided at base end portions of the wafer holding trays (see PTL 1). Each of the wafer holding trays moves up and down along the vertical shaft and rotates around the vertical shaft in a horizontal plane. The wafer holding trays of the pitch changing mechanism hold the entire lower surfaces of the plurality of semiconductor wafers at a position opposed to the foup to take out the plurality of semiconductor wafers at once. After the pitch changing mechanism has moved in a horizontal direction, the wafer holding trays move down, so that the pitch between the adjacent semiconductor wafers is shortened. Next, the wafer holding trays rotate around the vertical shafts to house all the semiconductor wafers in the processing shelf.